Orban 111b noise..........jeeeez

[Freq_Band]

Tip...before removing the electrolytic caps, mark on the pc board, the positive and negative sides of the cap orientation.
....this helps to prevent from installing then new ones backwards.

=FB=

[sethl]

I'm doing the same gentle mods to my 111b and I have a question regarding bypassing pins 4 + 8 on the OPA 2134.

On my unit (as on all of them?), the 4558 driver chips sit on a little daughter board above the motherboard. It appears that the closest path to ground is on the "bottom" of the 2 meg resistor off pin 2.

Is there some reason why using this as a path to ground is a bad idea? I know that in general it's good practice to have bypass caps as close as possible to both the chip and ground, and it seems like trying to reach the ground plane on the motherboard from the bypass caps would not be optimal....

Thanks much!

[Jim Williams]

If these changes don't remove the hum pickup, consider removing the power transformer and mounting it in a metal box. I would use 4 pin XLR's and a 4 conductor 18 awg cable to do that. Once that hum generator is removed, the hum should disappear.